本例完成的功能就是防止用户重复登录!若用户已经登录,则当其再次登录时,弹出提示框后返回!
实现思路:用户登录成功后,将用户登录信息存放到 Hashtable类型的Application["Online"]里面,其键值为SessionID,其Value值为用户ID;当用户注销时 ,调用Session.Abandon;在Global.asax里面的 SessionEnd事件中,将用户ID从Hashtable中删除;在用户访问页面时,察看Hashtable中是否有对应的用户ID如果没有则判断用户不在线(用户不在线的原因可能是按了注销按钮、网页超时等)
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深入思考:
由本例的解决方法可以加以延伸,比如,在存储 UserID的时候,将UserID+客户端IP地址一起存进去,则在将相应信息取出来分析的时候,可以做到:当用户在不同的计算机上先后登录的时候,则允许最近一 次的登录,而将之前的登录删除!等等等等